Coaxial cables are commonly utilized in RF communications systems. A typical coaxial cable includes an inner conductor, an outer conductor, a dielectric layer that separates the inner and outer conductors, and a jacket that covers the outer conductor. Coaxial cable connectors may be applied to terminate coaxial cables, for example, in communication systems requiring a high level of precision and reliability.
Coaxial connector interfaces provide a connect/disconnect functionality between (a) a cable terminated with a connector having a particular connector interface and (b) a corresponding connector with a mating connector interface mounted on an apparatus or on another cable. Typically, one connector will include a structure such as a pin or post connected to an inner conductor and an outer conductor connector body connected to the outer conductor; these are mated with a mating sleeve (for the pin or post of the inner conductor) and another outer conductor connector body of a second connector, wherein one of the outer conductor bodies fits within the other outer conductor body Coaxial connector interfaces often utilize a threaded coupling nut or other retainer that draws the connector interface pair into secure electro-mechanical engagement when the coupling nut (which is captured by one of the connectors) is threaded onto the other connector.
Passive Intermodulation Distortion (PIM) is a form of electrical interference/signal transmission degradation that may occur with less than symmetrical interconnections and/or as electro-mechanical interconnections shift or degrade over time. Interconnections may shift due to mechanical stress, vibration, thermal cycling, and/or material degradation. PIM can be an important interconnection quality characteristic, as PIM generated by a single low quality interconnection may degrade the electrical performance of an entire RF system. Thus, the reduction of PIM via connector design is typically desirable.
One manner of addressing PIM is to create connectors that capacitively couple when connected, rather than galvanically coupling through direct electrical contact in the manner of conventional connectors. In one example, the inner conductor post of one connector is covered with a dielectric layer, as is the outer surface of one of the outer conductors. When the two connectors are engaged, the dielectric layers insulate the conductors from each other, thereby creating a capacitive coupling between conductors. Capacitively coupled connectors may decrease PIM caused by minute debris contaminating the metallic connection normally found in mating RF connectors. Because physical contact is not required to couple RF energy through the interfaces, a major cause of contact debris, namely the contact force and wiping of the interfaces necessary for stable contact resistance, can be eliminated. An exemplary set of connectors of this type is shown in U.S. patent application Ser. No. 14/102,042, filed on Dec. 10, 2013, the disclosure of which is hereby incorporated herein in its entirety. However, other designs that employ capacitive coupling may also be desirable.